At a press briefing this morning, the union leader urged the government to “be strong enough” to absorb the controversy around some topics explored in PSHE, such as sex education, rather than leaving school leaders and teachers “exposed”.

Some parents have chosen to withdraw their children from classes, or have made “aggressive challenges and threats” to staff, around topics like homosexuality, the general secretary said.

Accusations of 'brainwashing'

Mr Hobby said: “We have seen really difficult situations with parents who disagree with the philosophies that are being raised. They say, ‘You’re doing this, you’re brainwashing our children’.

“It is really helpful for professionals in the front line who are very exposed to be able to say, ‘No, this is a duty and it is government regulation and every school in the country does it'.”

He added: “These are controversial topics that our society doesn’t wholly agree on and teachers have to be quite brave sometimes, I think, in [addressing these topics] and we should have their back when they do that.”

At the NAHT annual conference next week, the union will renew its calls for PSHE to be given a statutory status by the government in all schools.

Mr Hobby added: “We don’t think we need to make it statutory to make teachers do it. [We should] make it statutory to protect teachers when they do it because otherwise they are vulnerable to accusations that they are pursuing a personal agenda.”

The minister believes that making PSHE statutory would do little to tackle “the most pressing problems” with the subject.

Ahead of the union's annual conference in Birmingham next Friday, Mr Hobby said: “By not making it statutory I think the government is making teachers absorb the controversy when it really should be the government who is strong enough to absorb that.”

A Department for Education spokesperson said: “No teacher should be subjected to abuse or threats from parents. Where teachers are, we would urge them to report it to the relevant authority so the appropriate action can be taken.

“We want to provide all young people with a curriculum for life that prepares them to succeed in modern Britain. High quality teaching of PSHE is central to that and we expect all schools to teach it.

"We know that the vast majority of schools and teachers recognise the importance of PSHE, and trust teachers to tailor their lessons to best suit their pupils. We are focusing on raising the quality of PSHE teaching and working with leading headteachers and practitioners to look at how best to achieve this.”